It would be essentially impossible to create a new prion disease by accident- generating random-ish new things with methods like this would pale in comparison to the massive number of weird random-ish things natural biology is already creating in the wild.
However, this category of technologies could potentially be used to develop new prion diseases on purpose. As well as to develop cures for prion diseases that disrupt the misfolding.
>As well as to develop cures for prion diseases that disrupt the misfolding.
That seems quite plausible actually. You'd need something that can target misfolded PrP and bind it up so it can't do anything and then hopefully your targeting protein leaves normal PrP alone. A bit like an antibody.
The problem, from what I understand as a dabbler in protein research, is that PrP binds into these large very very stable semi crystalline fibers, (I visualize them looking like thick extruded complicated pasta shapes, where the 2d crosssection is kinda the shape of the outline of a single PrP). It makes it really hard to learn about the structure, actually, because x-ray crystallography requires repeated crystalline structures, and these are more like 3d polymer threads that bunch up and make things hard to image (though there's some more modern imaging techniques that are making headway). It turns out that these are very very stable configurations unfortunately and have very few ways to attach anything, and that's the precise problem with building binders. Plus, even worse, it turns out PrP might even be biologically necessary for mammals and we don't want to usually get rid of it wholesale [https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-01...]
However, this category of technologies could potentially be used to develop new prion diseases on purpose. As well as to develop cures for prion diseases that disrupt the misfolding.